Detection of viruses by electron microscopy: an efficient approach.

Wetting of grids is the most important aspect of the detection of viruses by electron microscopy. Carbon or plastic/carbon coated grids used in most electron microscopy laboratories are negatively charged and hydrophobic (Sogo, Portman, Kaufman and Koller, 1975. J. Microsc. 104, 187-198.). Most viruses are negatively charged at pH 6.0-7.0 which does not allow them to adhere effectively to the support film. Viruses are then washed away or form clumps on the grid making detection more difficult. A suitable wetting agent, 0.1% poly-L-lysine hydrobromide (MW 35000) has been used for the detection of plant viruses (Roberts, personal communication). This chemical was used for processing faecal samples from patients with gastroenteritis for electron microscopy. The result showed a significant increase in terms of virus concentration on the grids and an increase in the general detection rate of positive samples. A study was then undertaken comparing the treatment method of grids using faecal samples. The grids were treated and not treated with poly-L-lysine hydrobromide.